Conventionally, many systems have been proposed in which a listener enjoys listening to a stereophonic sound field by wearing a headphone. These systems are mainly based on the principle that the sound arrived at eardrums is controlled to reproduce the original sound field. However, since the distance from the external ears to the eardrums are largely different every individual, the sound field to be localized in the front may sometimes shift to the rear, which dulls the sense of distance.
In addition, there have been devised techniques in which, by utilizing speakers in a room or inside a vehicle compartment, the arriving time of the sound waves from the speakers to a listener is made even to control the position of the image, or in which a transfer characteristic is convoluted into the input signal to be inputted to the speakers to control the sound field. However, these techniques have shortcomings that they are valid only within a small listening area and are for instance effective only for one listener who sits on a target seat inside the vehicle compartment (hereinafter also referred to as the seat). Still further, these techniques exert a different effect that largely varies depending on a situation where other listeners are seated inside the vehicle and a situation where nobody is.
This invention has been made to solve the above-described and other problems, and has an object of providing a vehicle-mounted three dimensional sound field reproducing unit which enables reproduction of a) a sound field with high accuracy and fidelity near the external ears of the listener without wearing a headphone, and b) a sound field with high accuracy and fidelity as compared with the conventional headphone having one speaker per one ear, as a result of adoption of at least two or more speakers (i.e., four or more speakers for both the ears).